Core drill



(5. O. SUMAN CORE DRILL Filed March 13, 1928 m ma 0 f, w 6 q ATTOENE) A/ll l atentcd ec. EQEBE enonen 0. so, or car. cnnran, cauronnm, ASSIGNORT Assocmriao on. comrm, or SAN rorsco, CALIFORNIA, A CORPORATION; orcmroaam cone L Application aia Mai-011 13, 1928. Serial No. 261,323.

This invention relates to core drills adapted to be used to determinegeological formations, and contemplates the provision of a tool, havinga novel form of core barrel.

The object of this invention is to construct a tool of the characterreferred to, which is designed primarily to produce better and longercores under all conditions.

The present practice is to bring the core 1 barrels to the surface,unscrew the three foot sections, and extract the core from each section.Thecores are often tightly wedged in the barrels and it is necessary toforce the core up with a screw auger, and in some cases it is evennecessary to split the barrel with an acetylene torch. In view of suchconditions,

it is easily seen that there is a great amount I offriction between thecore and the barrel, and the longer the core the greater the friction.This frictional resistance prevents the taking of longer cores and alsoexplains the failure in some instances to core sand, because .the patharound the outside of the core bit ofiers less resistance than the corebarrel.

It is therefore a further object of this invention to reduce thisfrictional resistance between the core and the barrel.

Briefly, this may be accomplished by increasing in an upwardly directionthe cross 0 section of the inner core barrel, so that an increase in thelength of the core will tend to reduce the frictional resistance in thecore barrel. This friction may also be reducedby perforating the corebarrel, so that some of the mud coating on the core may escape throughthe holes and be carried out by the circulating liquid.

Other objects and advantages of this invention will be apparent from thefollowing 40 description, taken in conjunction with the accompanyingdrawing, in which:

The figure represents a vertical section of a core drill, embodying thefeatures of this invention. v. In the drawing, the numeral 1 representsa drill pipe which is of constant cross section and to which is attacheda core bit 2, which may be of any type now used by those skilled in theart. Within the drill pipe 1 there is an 60 outer core barrel 3, also ofconstant diameter,

which is provided at its bottom with passages 4 and5, which communicatewith the interior of the barrel., i Within this outer core barrel 3there is an inner core barrel 6 having perforations 7 therein and whosecross section decreases gradually from the top down to the core bit 2.In addition, the core barrel 6 is provided with an openin 13 at the topto allow the mud-laden flui in the core barrel to escape as the core isbeing taken and thereby preveint an increase of pressure within thebarre In operation, mud-laden fluid is circulated down the interior ofthe drill pipe under pressure and passes between the drill pipe and theouter core barrel 3 in the direction of the arrows. "At the bottom, partof this fluid passes out of the drill pipe through thepassages 8 and 9and upwardly in the direction of the arrows, while the other part passesthrough the passages 4i and 5 and is circulated upwardly in thedirection of the arrows between the core barrels. The valve 10, which isdiagrammatically illustrated, allows the mud-laden fluid which has beencirculated between the core barrels, to pass through the pipe '11 andfinally become discharged through the outlet 12 in the drill pipe 1.

It should be remembered in the construction of this inner corebarrel-that the bottom section of the barrel should have a very slighttape-r, and in fact, in some instances it maybe advisable to allow thediameter to remain unchanged, for the reason that if the friction isreduced "beyond a certain point the core may be lost when the drill pipeis withdrawn. i

This particular type of core drill presents many advantages over thetypes now in use.

Naturally, the gradual increase upwardly in the cross section of theinner core barrel reduces the undesirable resistance as the core becomeslonger, which" is just the opposite of the condition encountered at thepresent time. The circulation of mud-laden fluid upward between theinner and the outer core barrels definitely and positively does awaywith any downward thrust on or in the core barrel. The perforations onthe inner core 10 barrel release the frictional strain set up in thecore barrel by mud-laden fluid, and in addition the friction is reducedby the slight upward force of the movin laden fluid on the outside 0 theinner barrel.

With the improvements herein mentioned embodied in a core drill, it isnow possible to obtain longer and better cores, to the extent that thelength of the cores taken will be at least double those which are nowtaken by the present core drills.

This reduction of the pressure of the mud coat against the actualformation core, due to the release of pressure by perforationspermitting the escape of mud-laden fluid and also the increase indiameter of the core bar-, rel as the core rises in the barrel naturallybrings up the question as to what happens to the formation core whenthis occurs. In the case of shale, nothing happens, as the shale issufiiciently hard and compact to resist any minor forces of theformation core above coming into the barrel from below to compress it.In the case of loose sand or soft clay, there may be a slight tendencyto compress or spread out, but this is overcome somewhat by the mudcoating and also by the upward lifting pressure exerted by the movementof the mud-laden column of fluid, which is continually in efiect outsidethe inner barrel.

Having now more particularly described my invention, what I claim is:

1.111 a core drill, a drill pipe, a second column of mudneeeaso drillpipe, a second pipe within the drill pipe and spaced therefrom, aperforated core barrel within the second pipe and spaced therefrom, andmeans for positively circulating liquid upwardly from the interior ofthe drill pipe between said second pipe and core barrel to the exteriorof the drill pipe.

6. In a core drill the combination of; a drill pipe, a second pipewithin the drill pipe and spaced therefrom, a valved discharge passagefrom the top of said second pipe to the exterior of the drill pipe, acore barrel within the second pipe and spaced therefrom, and means forpassing liquid upwardly from the interior of the drill pipe between saidsecond pipe and core barrel. v

7. in a core drill .the combination of: a drill pipe, a second pipewithin the drill pipe and spaced therefrom, a tapered perforated corebarrel with the second pipe and spaced therefrom, a valved dischargepassage from the top of said second pipe to the exterior of the drillpipe, and means for passing liquid from the drill pipe between saidsecond pipe and core barrel.

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pipe within the drill pipe and spaced therefrom, a perforated corebarrel tapering downwardly within said second pipe and spaced therefrom,and means for circulating liquid between the drill pipe and the corebarrel.

2. In a core drill, a drill pipe, a second pipe within the drill pipeand spaced therefrom, a perforated core barrel tapering downwardlywithin said second pipe and spaced therefrom, and passages connectingthe interior of the drill pipe to the interior of the second pipe,whereby mud-laden fluids may be circulated upwardly between the corebarrel and said second pipe.

3. In a core drill the combination of: a drill pipe, a second pi ewithin the drill pipe and spaced there rom, a bore barrel within thesecond pipe and spaced therefrom,

and means for positively circulating liquid upwardly from the interiorof the drill pipe between said second pipe and corebarrel.

4. In a core drill the combination of: a drill pipe, a second pipewithin the drill pipe and spaced therefrom, a core barrel within thesecond pipe and spaced therefrom,

and means forpositively circulating liquid upwardly from the interior ofthe drill pipe between said second pipe and core barrel to the exteriorof the drill pipe.

5. In a core drill the combination of: a

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